Green smoothies are my main kind of smoothie. I usually pack'em full of stuff and it's pretty sweet!
What I usually put in it: banana, strawberries, orange, water, baby spinach, greenleaf lettuce, sometimes romaine lettuce, a little agave. grinded flax seed, sprouts and a little ice at the end to get it nice and cold.
i sometimes added a peeled cucumber (wonderful for your skin), apple, a collard leaf or two.
sometimes i throw ALL of that in there. it makes a huge amount but i put the rest in the fridge for later.
when i do a simple one, i put a couple different kinds of fruit and some baby spinach in it. I pretty much never have a smoothie without some sort of leafy green added.
They do have these 'savory smoothie' recipes out and about. They're like a soup, I guess. People add ginger, garlic, peppers, that sorta thing. I haven't been brave enough to try one of those yet, though.